| 1. |
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| 2. |
- Kaur-Kahlon, G., et al.
(författare)
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Response of a coastal tropical pelagic microbial community to changed salinity and temperature
- 2016
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Ingår i: Aquatic Microbial Ecology. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
-
Tidskriftsartikel (refereegranskat)abstract
- Studies on the responses of tropical microbial communities to changing hydrographic conditions are presently poorly represented. We present here the results from a mesocosm experiment conducted in southwest (SW) coastal India to investigate how changes in temperature and salinity may affect a coastal tropic microbial community. The onset of algal and bacterial blooms, the maximum production and biomass, and the interrelation between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up featuring ambient conditions (28 °C, 35 PSU), hyposalinity (31 PSU), warming (31 °C) and a double manipulated treatment with warming and hyposalinity (31 °C, 31 PSU). The hyposaline treatment had the most considerable influence manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulated treatment and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model approach, and found a significant interrelation between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation with subsequent significant effects on the quantity of microbial biomass and production.
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| 3. |
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| 4. |
- Kumar, S., et al.
(författare)
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Nitrogen uptake potential under different temperature-salinity conditions: Implications for nitrogen cycling under climate change scenarios
- 2018
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Ingår i: Marine Environmental Research. - : Elsevier BV. - 0141-1136 .- 1879-0291. ; 141:October, s. 196-204
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Tidskriftsartikel (refereegranskat)abstract
- As projected by climate change models, increase in sea surface temperature and precipitation in the future may alter nutrient cycling in the coastal regions due to potential changes in phytoplankton community structure and their ability to assimilate nitrogen (N) and carbon (C). An experiment simulating different temperature and salinity conditions (28 degrees C-35 ambient conditions, 28 degrees C-31, 31 degrees C-35 and 31 degrees C-31) in mesocosms containing 1000 L of coastal water from the Arabian Sea was performed and N uptake rates were measured using N-15 tracer technique on 2nd, 5th, 7th and 10th day of the experiment. The results show that, under all conditions, the total N (NO3- + NH4+) uptake rates were lower in the beginning and on the final day of the tracer experiment, while it peaked during middle, consistent with chlorophyll a concentrations. Total N uptake rate was significantly lower (p = 0.003) under ambient temperature -lower salinity condition (28 degrees C-31) than the others. This indicates that lowering of salinity in coastal regions due to excessive rainfall in the future may affect the N uptake potential of the phytoplankton, which may change the regional C and N budget.
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| 5. |
- Panova, M, et al.
(författare)
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DNA Extraction Protocols for Whole-Genome Sequencing in Marine Organisms
- 2016
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Ingår i: Marine Genomics - Methods and Protocols. - New York, NY : Springer New York. - 1064-3745. - 9781493937745 - 9781493937721 ; 1452, s. 13-44
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Bokkapitel (refereegranskat)abstract
- The marine environment harbors a large proportion of the total biodiversity on this planet, including the majority of the earths’ different phyla and classes. Studying the genomes of marine organisms can bring interesting insights into genome evolution. Today, almost all marine organismal groups are understudied with respect to their genomes. One potential reason is that extraction of high-quality DNA in sufficient amounts is challenging for many marine species. This is due to high polysaccharide content, polyphenols and other secondary metabolites that will inhibit downstream DNA library preparations. Consequently, protocols developed for vertebrates and plants do not always perform well for invertebrates and algae. In addition, many marine species have large population sizes and, as a consequence, highly variable genomes. Thus, to facilitate the sequence read assembly process during genome sequencing, it is desirable to obtain enough DNA from a single individual, which is a challenge in many species of invertebrates and algae. Here, we present DNA extraction protocols for seven marine species (four invertebrates, two algae, and a marine yeast), optimized to provide sufficient DNA quality and yield for de novo genome sequencing projects.
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| 6. |
- Ellegaard, M., et al.
(författare)
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Dead or alive: sediment DNA archives as tools for tracking aquatic evolution and adaptation
- 2020
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Ingår i: Communications Biology. - : Springer Science and Business Media LLC. - 2399-3642. ; 3:1
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Tidskriftsartikel (refereegranskat)abstract
- DNA can be preserved in marine and freshwater sediments both in bulk sediment and in intact, viable resting stages. Here, we assess the potential for combined use of ancient, environmental, DNA and timeseries of resurrected long-term dormant organisms, to reconstruct trophic interactions and evolutionary adaptation to changing environments. These new methods, coupled with independent evidence of biotic and abiotic forcing factors, can provide a holistic view of past ecosystems beyond that offered by standard palaeoecology, help us assess implications of ecological and molecular change for contemporary ecosystem functioning and services, and improve our ability to predict adaptation to environmental stress. Ellegaard et al. discuss the potential for using ancient environmental DNA (eDNA), combined with resurrection ecology, to analyse trophic interactions and evolutionary adaptation to changing environments. Their Review suggests that these techniques will improve our ability to predict genetic and phenotypic adaptation to environmental stress.
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| 7. |
- Godhe, Anna, 1967, et al.
(författare)
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Comparison of three common molecular tools for distinguishing among geographically separated clones of the diatom Skeletonema marinoi Sarno et Zingone (bacillariophyceae)
- 2006
-
Ingår i: Journal of Phycology. - : Wiley. - 0022-3646 .- 1529-8817. ; 42:2, s. 280-291
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Tidskriftsartikel (refereegranskat)abstract
- Skeletonema marinoi Sarno et Zingone is a planktonic marine diatom with a widespread geographic distribution. Different populations of this species may show distinct genetic signatures. We have evaluated the utility of three common molecular methods for distinguishing clones of S. marinoi from different geographic regions. Clonal cultures were isolated from the Canadian west coast, south west Portugal, and the east and west coasts of Sweden. All strains originated from resting stages in sediment. More than 90% of the individually isolated chains grew to densities suitable for DNA extraction. Genetic signatures of clones from each sample location were assessed by sequencing variable domains (D1-D3) of the nuclear large subunit (LSU) rRNA gene and internal transcriber spacer (ITS) (ITS-1, 5.8S and ITS-2) regions, and also by analysis of randomly amplified polymorphic DNA patterns. Analysis of molecular variance showed that strains from the four geographic areas were significantly separated by all three methods but that differences among European samples were best resolved by ITS 2 sequences.
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| 8. |
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| 9. |
- Godhe, Anna, 1967, et al.
(författare)
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Intercalibration of classical and molecular techniques for identification of Alexandrium fundyense (Dinophyceae) and estimation of cell densities
- 2007
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Ingår i: Harmful Algae. - : Elsevier BV. - 1568-9883. ; 6:1, s. 56-72
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Tidskriftsartikel (refereegranskat)abstract
- A workshop with the aim to compare classical and molecular techniques for phytoplankton enumeration took place at Kristineberg Marine Research Station, Sweden, in August 2005. Seventeen different techniques - nine classical microscopic-based and eight molecular methods - were compared. Alexandrium fundyense was the target organism in four experiments. Experiment 1 was designed to determine the range of cell densities over which the methods were applicable. Experiment 2 tested the species specificity of the methods by adding Alexandrium ostenfeldii, to samples containing A. fundyense. Experiments 3 and 4 tested the ability of the methods to detect the target organism within a natural phytoplankton community. Most of the methods could detect cells at the lowest concentration tested, 100 cells L-1, but the variance was high for methods using small volumes, such as counting chambers and slides. In general, the precision and reproducibility of the investigated methods increased with increased target cell concentration. Particularly molecular methods were exceptions in that their relative standard deviation did not vary with target cell concentration. Only two of the microscopic methods and three of the molecular methods had a significant linear relationship between their cell count estimates and the A. fundyense concentration in experiment 2, where the objective was to discriminate that species from a morphologically similar and genetically closely related species. None of the investigated methods were affected by the addition of a natural plankton community background matrix in experiment 3. The results of this study are discussed in the context of previous intercomparisons and the difficulties in defining the absolute, true target cell concentration. (c) 2006 Elsevier B.V. All rights reserved.
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| 10. |
- Kaur-Kahlon, Gurpreet, et al.
(författare)
-
Response of a coastal tropical pelagic microbial community to changed salinity and temperature
- 2016
-
Ingår i: Aquatic Microbial Ecology. - : Inter-Research Science Center. - 0948-3055 .- 1616-1564. ; 77:1, s. 37-50
-
Tidskriftsartikel (refereegranskat)abstract
- Studies on the responses of tropical microbial communities to changing hydrographic conditions are poorly represented. We present here the results from a mesocosm experiment conducted in coastal southwestern India to investigate how changes in temperature and salinity may affect a coastal tropical microbial community. The onset of algal and bacterial blooms, maximum production and biomass, and the interrelationship between phytoplankton and bacteria were studied in replicated mesocosms. The treatments were set up to feature ambient conditions (28°C, 35 PSU), hyposalinity (31 PSU), warming (31°C), and a double manipulation treatment with warming and hyposalinity (31°C, 31 PSU). The hyposaline treatment had the most considerable influence, manifested as significantly lower primary production, and the most dissimilar microphytoplankton species community. The increased temperature acted as a catalyst in the double manipulation treatment, and higher primary production was maintained. We investigated the dynamics of the microbial community with a structural equation model and found a significant interrelationship between phytoplankton biomass and bacterial abundance. Using this methodology, it became evident that temperature and salinity changes, individually and together, mediate direct and indirect effects that influence different compartments of the microbial loop. In the face of climate change, we suggest that in relatively nutrient-replete tropical coastal zones, salinity and temperature changes will affect nutrient assimilation, with subsequent significant effects on the quantity of microbial biomass and production.
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| 11. |
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| 12. |
- Kremp, A, et al.
(författare)
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Intraspecific variability in the response of bloom forming marine microalgae to changed climatic conditions
- 2012
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 2:6, s. 1195-1207
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Tidskriftsartikel (refereegranskat)abstract
- Phytoplankton populations can display high levels of genetic diversity that, when reflected by phenotypic variability, may stabilize a species response to environmental changes. We studied the effects of increased temperature and CO2 availability as predicted consequences of global change, on 16 genetically different isolates of the diatom Skeletonema marinoi from the Adriatic Sea and the Skagerrak (North Sea), and on eight strains of the PST (paralytic shellfish toxin)-producing dinoflagellate Alexandrium ostenfeldii from the Baltic Sea. Maximum growth rates were estimated in batch cultures of acclimated isolates grown for five to 10 generations in a factorial design at 20 and 24°C, and present day and next century applied atmospheric pCO2, respectively. In both species, individual strains were affected in different ways by increased temperature and pCO2. The strongest response variability, buffering overall effects, was detected among Adriatic S. marinoi strains. Skagerrak strains showed a more uniform response, particularly to increased temperature, with an overall positive effect on growth. Increased temperature also caused a general growth stimulation in A. ostenfeldii, despite notable variability in strain-specific response patterns. Our data revealed a significant relationship between strain-specific growth rates and the impact of pCO2 on growth—slow growing cultures were generally positively affected, while fast growing cultures showed no or negative responses to increased pCO2. Toxin composition of A. ostenfeldii was consistently altered by elevated temperature and increased CO2 supply in the tested strains, resulting in overall promotion of saxitoxin production by both treatments. Our findings suggest that phenotypic variability within populations plays an important role in the adaptation of phytoplankton to changing environments, potentially attenuating short-term effects and forming the basis for selection. In particular, A. ostenfeldii blooms may expand and increase in toxicity under increased water temperature and atmospheric pCO2 conditions, with potentially severe consequences for the coastal ecosystem.
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| 13. |
- Pinseel, E., et al.
(författare)
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Strain-specific transcriptional responses overshadow salinity effects in a marine diatom sampled along the Baltic Sea salinity cline
- 2022
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Ingår i: Isme Journal. - : Springer Science and Business Media LLC. - 1751-7362 .- 1751-7370.
-
Tidskriftsartikel (refereegranskat)abstract
- The salinity gradient separating marine and freshwater environments represents a major ecological divide for microbiota, yet the mechanisms by which marine microbes have adapted to and ultimately diversified in freshwater environments are poorly understood. Here, we take advantage of a natural evolutionary experiment: the colonization of the brackish Baltic Sea by the ancestrally marine diatom Skeletonema marinoi. To understand how diatoms respond to low salinity, we characterized transcriptomic responses of acclimated S. marinoi grown in a common garden. Our experiment included eight strains from source populations spanning the Baltic Sea salinity cline. Gene expression analysis revealed that low salinities induced changes in the cellular metabolism of S. marinoi, including upregulation of photosynthesis and storage compound biosynthesis, increased nutrient demand, and a complex response to oxidative stress. However, the strain effect overshadowed the salinity effect, as strains differed significantly in their response, both regarding the strength and the strategy (direction of gene expression) of their response. The high degree of intraspecific variation in gene expression observed here highlights an important but often overlooked source of biological variation associated with how diatoms respond to environmental change.
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| 14. |
- Turner, Lucy M., et al.
(författare)
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Toxic Algae Silence Physiological Responses to Multiple Climate Drivers in a Tropical Marine Food Chain
- 2019
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Ingår i: Frontiers in Physiology. - : Frontiers Media SA. - 1664-042X. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Research on the effects of climate change in the marine environment continues to accelerate, yet we know little about the effects of multiple climate drivers in more complex, ecologically relevant settings - especially in sub-tropical and tropical systems. In marine ecosystems, climate change (warming and freshening from land run-oft) will increase water column stratification which is favorable for toxin producing dinoflagellates. This can increase the prevalence of toxic microalgal species, leading to bioaccumulation of toxins by filter feeders, such as bivalves, with resultant negative impacts on physiological performance. In this study we manipulated multiple climate drivers (warming, freshening, and acidification), and the availability of toxic microalgae, to determine their impact on the physiological health, and toxin load of the tropical filter-feeding clam, Meretrix meretrix. Using a structural equation modeling (SEM) approach, we found that exposure to projected marine climates resulted in direct negative effects on metabolic and immunological function and, that these effects were often more pronounced in clams exposed to multiple, rather than single climate drivers. Furthermore, our study showed that these physiological responses were modified by indirect effects mediated through the food chain. Specifically, we found that when bivalves were fed with a toxin-producing dinoflagellate (Alexandrium minutum) the physiological responses, and toxin load changed differently and in a non-predictable way compared to clams exposed to projected marine climates only. Specifically, oxygen consumption data revealed that these clams did not respond physiologically to climate warming or the combined effects of warming, freshening and acidification. Our results highlight the importance of quantifying both direct and, indirect food chain effects of climate drivers on a key tropical food species, and have important implications for shellfish production and food safety in tropical regions.
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| 15. |
- Cardinale, Daniele A., 1982-, et al.
(författare)
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Enhanced Skeletal Muscle Oxidative Capacity and Capillary-to-Fiber Ratio Following Moderately Increased Testosterone Exposure in Young Healthy Women
- 2020
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Ingår i: Frontiers in Physiology. - : Frontiers Media S.A.. - 1664-042X. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recently, it was shown that exogenously administered testosterone enhances endurance capacity in women. In this study, our understanding on the effects of exogenous testosterone on key determinants of oxygen transport and utilization in skeletal muscle is expanded.Methods: In a double-blinded, randomized, placebo-controlled trial, 48 healthy active women were randomized to 10 weeks of daily application of 10 mg of testosterone cream or placebo. Before and after the intervention, VO2 max, body composition, total hemoglobin (Hb) mass and blood volumes were assessed. Biopsies from the vastus lateralis muscle were obtained before and after the intervention to assess mitochondrial protein abundance, capillary density, capillary-to-fiber (C/F) ratio, and skeletal muscle oxidative capacity.Results: Maximal oxygen consumption per muscle mass, Hb mass, blood, plasma and red blood cell volumes, capillary density, and the abundance of mitochondrial protein levels (i.e., citrate synthase, complexes I, II, III, IV-subunit 2, IV-subunit 4, and V) were unchanged by the intervention. However, the C/F ratio, specific mitochondrial respiratory flux activating complex I and linked complex I and II, uncoupled respiration and electron transport system capacity, but not leak respiration or fat respiration, were significantly increased following testosterone administration compared to placebo.Conclusion: This study provides novel insights into physiological actions of increased testosterone exposure on key determinants of oxygen diffusion and utilization in skeletal muscle of women. Our findings show that higher skeletal muscle oxidative capacity coupled to higher C/F ratio could be major contributing factors that improve endurance performance following moderately increased testosterone exposure.
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| 16. |
- Ferrante, M. I., et al.
(författare)
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Exploring Molecular Signs of Sex in the Marine Diatom Skeletonema marinoi
- 2019
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Ingår i: Genes. - : MDPI AG. - 2073-4425. ; 10:7
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Tidskriftsartikel (refereegranskat)abstract
- Sexual reproduction plays a fundamental role in diatom life cycles. It contributes to increasing genetic diversity through meiotic recombination and also represents the phase where large-sized cells are produced to counteract the cell size reduction process that characterizes these microalgae. With the aim to identify genes linked to the sexual phase of the centric planktonic diatom Skeletonema marinoi, we carried out an RNA-seq experiment comparing the expression level of transcripts in sexualized cells with that of large cells not competent for sex. A set of genes involved in meiosis were found upregulated. Despite the fact that flagellate gametes were observed in the sample, we did not detect the expression of genes involved in the synthesis of flagella that were upregulated during sexual reproduction in another centric diatom. A comparison with the set of genes changing during the first phases of sexual reproduction of the pennate diatom Pseudo-nitzschia multistriata revealed the existence of commonalities, including the strong upregulation of genes with an unknown function that we named Sex Induced Genes (SIG). Our results further broadened the panel of genes that can be used as a marker for sexual reproduction of diatoms, crucial for the interpretation of metatranscriptomic datasets.
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| 17. |
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| 18. |
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| 19. |
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| 20. |
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| 21. |
- Godhe, Anna, 1967, et al.
(författare)
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Quantification of Diatom and Dinoflagellate Biomasses in Coastal Marine Seawater Samples by Real-Time PCR
- 2008
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Ingår i: Applied and Environmental Microbiology. - 0099-2240. ; 74:23, s. 7174-7182
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Tidskriftsartikel (refereegranskat)abstract
- Two real-time PCR assays targeting the small-subunit (SSU) ribosomal DNA (rDNA) were designed to assess the proportional biomass of diatoms and dinoflagellates in marine coastal water. The reverse primer for the diatom assay was designed to be class specific, and the dinoflagellate-specific reverse primer was obtained from the literature. For both targets, we used universal eukaryotic SSU rDNA forward primers. Specificity was confirmed by using a BLAST search and by amplification of cultures of various phytoplankton taxa. Reaction conditions were optimized for each primer set with linearized plasmids from cloned SSU rDNA fragments. The number of SSU rDNA copies per cell was estimated for six species of diatoms and nine species of dinoflagellates; these were significantly correlated to the biovolumes of the cells. Nineteen field samples were collected along the Swedish west coast and subjected to the two real-time PCR assays. The linear regression of the proportion of SSU rDNA copies of dinoflagellate and diatom origin versus the proportion of dinoflagellate and diatom biovolumes or biomass per liter was significant. For diatoms, linear regression of the number of SSU rDNA copies versus biovolumes or biomass per liter was significant, but no such significant correlation was detected in the field samples for dinoflagellates. The method described will be useful for estimating the proportion of dinoflagellate versus diatom biovolume or biomass and the absolute diatom biovolume or biomass in various aquatic disciplines.
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| 22. |
- Härnström, Karolina, 1980, et al.
(författare)
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Tropical phytoplankton community development in mesocosms inoculated with different life stages
- 2007
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Ingår i: Marine Ecology-Progress Series. - : Inter-Research Science Center. - 0171-8630 .- 1616-1599. ; 346, s. 75-88
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Tidskriftsartikel (refereegranskat)abstract
- Many diatom species have the ability to form benthic resting stages, but the importance of these stages as a supply for planktonic blooms is uncertain. A mesocosm study was carried out in December 2005 to January 2006 in Mangalore, India. Mesocosms were inoculated with various combinations of benthic and/or planktonic cells, sampled from the coastal SE Arabian Sea, and the development of the planktonic community was followed. Diatoms dominated the phytoplankton community in all mesocosms, irrespective of inoculum. The most significant differences among inoculum types were altered species composition, and the timings of the maximum cell abundances, which lagged behind in the sediment mesocosms. Populations of Thalassiosira were initiated by both plankton and benthic propagules. Taxa known from temperate coastal areas to seed bloom by benthic propagules, such as Chaetoceros and Skeletonema, were predominantly seeded by planktonic cells in this experiment; this implies differential seeding strategy within the same species at different latitudes. The species assemblage encountered in the plankton and sediment was similar, which indicates that the benthic resting stages seed an autochthonous phytoplankton flora in the area. High species diversity in all inoculated mesocosms was maintained throughout the experimental period, although the actual number of species was fewer at the end. The hydrographic conditions and timing of formation, survival, and germination of diatom resting stages in SE Arabian Sea are discussed.
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| 23. |
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| 24. |
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| 25. |
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| 26. |
- Pelusi, A., et al.
(författare)
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The diatom Chaetoceros socialis: spore formation and preservation
- 2020
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Ingår i: European Journal of Phycology. - : Informa UK Limited. - 0967-0262 .- 1469-4433. ; 55:1, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Planktonic diatoms thrive in the water column, and several species can transform into resting stages - spores or resting cells - that sink to the bottom of the sea. Resting stages are generally produced when environmental conditions are not optimal for growth and can remain viable in sediments for a long time. We tested different aspects related to the formation of spores in Chaetoceros socialis, one of the dominant diatoms in the Gulf of Naples (Mediterranean Sea, Italy). Observations in time lapse and confocal laser scanning microscopy allowed illustration of the formation of endogenous spores, in which valve deposition is accompanied by an acytokinetic nuclear division. The complete transition from vegetative cell to spore takes about 8-10 h and, if exposed to the light, spores can germinate again after a few days. The depletion of nitrogen source in the culture medium induced the formation of spores, with very similar dynamics among different sympatric strains; extremely high percentages of spores (up to >95%) were produced after 4-5 days. Once formed, spores can remain viable for up to nine months, and anoxic conditions favour their preservation. Identical dynamics of spore formation were detected in freshly established cultures and in cultures produced by the germination of spores kept dormant for different lengths of time. Our results suggest that spores of C. socialis can, in principle, rapidly shift between vegetative cells and resting stages that may explain the success of this species in coastal water. Our results also demonstrate that storage of resting spores may represent an alternative to cryopreservation.
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| 27. |
- Rehnstam-Holm, Ann-Sofi, 1959, et al.
(författare)
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Association between Phytoplankton and Vibrio spp along the southwest coast of India- a mesocosm experiment.
- 2010
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Ingår i: Aquatic Microbial Ecology. - : Inter-Research. - 0948-3055 .- 1616-1564. ; 58, s. 127-139
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Tidskriftsartikel (refereegranskat)abstract
- We report the results from a mesocosm study investigating the interrelationship between microalgae and vibrios. The mesocosms were inoculated with plankton, plankton + sediment, or sediment. We followed the diatom bloom and increases in the abundance of Vibrio spp. and V parahaemolyticus in conjunction with several environmental variables in all mesocosms and at a reference site. The dominating diatom genera were also identified. Temperature, salinity, and pH were nearly invariant in the mesocosms and did not contribute to the results. The principal environmental variables that correlated to vibrio abundance were total bacterial plate counts, phosphorus and ammonia (positive relationship), and oxygen and silica (negative). Nitrate, total bacterial counts and chlorophyll a (chl a) did not correlate with vibrio growth. The highest diatom abundances were followed by increases in vibrios in all mesocosms. This was also observed in field sampling. Together, these results suggest that diatom blooms could support Vibrio spp. growth. V parahaemolyticus was initially favoured by sediment. The contribution of V parahaemolyticus to the total bacterial population was low, on average 0.5 %, but constituted a rather high proportion of the vibrio population in the mesocosm systems, i.e. on average 18 %. Some of the identified diatom genera, e.g. Chaetoceros and Skeletonema, were negatively correlated to vibrios, while Coscinodiscus was positively correlated. The results indicate that phytoplankton blooms, when recorded as high levels of chl a, should be used with caution as predictors for future vibrio epidemics, since the origin of the chl a might have a significant effect on vibrio abundance.
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| 28. |
- Rehnstam-Holm, Ann-Sofi, 1959-, et al.
(författare)
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Defining the niche of Vibrio parahaemolyticus during pre- and post-monsoon seasons in the coastal Arabian Sea
- 2014
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Ingår i: Microbial Ecology. - 0095-3628 .- 1432-184X. ; 67:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- The bacteria Vibrio parahaemolyticus is an important component of coastal ecosystems worldwide, and in recent years, V. parahaemolyticus has caused several cases of food-borne gastroenteritis. However, research investigating which parameters are important in regulating V. parahaemolyticus abundance in tropical areas with relatively stable temperatures and salinity are largely lacking. The objective here was to investigate which environmental forces are driving elevated abundances of V. parahaemolyticus in a tropical oligotrophic coastal area in the Arabian Sea. We analysed a large number of environmental parameters in parallel with cell densities of V. parahaemolyticus and Vibrio spp. Abundance data was obtained using real-time PCR, during two different sampling periods, representative for two distinct seasons. Water temperature and salinity were stable during and between sampling periods, but V. parahaemolyticus abundances were on average six times higher during the first sampling period in December, compared to the second period in February–March. V. parahaemolyticus abundance was found to be positively correlated to inorganic phosphate concentration and copepod abundance. We thus hypothesise that these are important factors regulating V. parahaemolyticus abundance in coastal tropical areas during these periods.
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| 29. |
- Rehnstam-Holm, Ann-Sofi, et al.
(författare)
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Defining the niche of Vibrio parahaemolyticus during pre- and post-monsoon seasons in the coastal Arabian Sea
- 2014
-
Ingår i: Microbial Ecology. - : Springer New York. - 0095-3628 .- 1432-184X. ; 67:1, s. 57-65
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Tidskriftsartikel (refereegranskat)abstract
- The bacteria Vibrio parahaemolyticus is an important component of coastal ecosystems worldwide, and in recent years, V. parahaemolyticus has caused several cases of food-borne gastroenteritis. However, research investigating which parameters are important in regulating V. parahaemolyticus abundance in tropical areas with relatively stable temperatures and salinity are largely lacking. The objective here was to investigate which environmental forces are driving elevated abundances of V. parahaemolyticus in a tropical oligotrophic coastal area in the Arabian Sea. We analysed a large number of environmental parameters in parallel with cell densities of V. parahaemolyticus and Vibrio spp. Abundance data was obtained using real-time PCR, during two different sampling periods, representative for two distinct seasons. Water temperature and salinity were stable during and between sampling periods, but V. parahaemolyticus abundances were on average six times higher during the first sampling period in December, compared to the second period in February–March. V. parahaemolyticus abundance was found to be positively correlated to inorganic phosphate concentration and copepod abundance. We thus hypothesise that these are important factors regulating V. parahaemolyticus abundance in coastal tropical areas during these periods.
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| 30. |
- Sefbom, Josefin, et al.
(författare)
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A planktonic diatom displays genetic structure over small spatial scales
- 2018
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Ingår i: Environmental Microbiology. - : Wiley. - 1462-2912 .- 1462-2920. ; 20:8, s. 2783-2795
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Tidskriftsartikel (refereegranskat)abstract
- Marine planktonic microalgae have potentially global dispersal, yet reduced gene flow has been confirmed repeatedly for several species. Over larger distances (>200 km) geographic isolation and restricted oceanographic connectivity have been recognized as instrumental in driving population divergence. Here we investigated whether similar patterns, that is, structured populations governed by geographic isolation and/or oceanographic connectivity, can be observed at smaller (6-152 km) geographic scales. To test this we established 425 clonal cultures of the planktonic diatom Skeletonema marinoi collected from 11 locations in the Archipelago Sea (northern Baltic Sea). The region is characterized by a complex topography, entailing several mixing regions of which four were included in the sampling area. Using eight microsatellite markers and conventional F-statistics, significant genetic differentiation was observed between several sites. Moreover, Bayesian cluster analysis revealed the co-occurrence of two genetic groups spread throughout the area. However, geographic isolation and oceanographic connectivity could not explain the genetic patterns observed. Our data reveal hierarchical genetic structuring whereby despite high dispersal potential, significantly diverged populations have developed over small spatial scales. Our results suggest that biological characteristics and historical events may be more important in generating barriers to gene flow than physical barriers at small spatial scales.
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| 31. |
- Sefbom, Josefin, et al.
(författare)
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Local adaptation through countergradient selection in northern populations of Skeletonema marinoi
- 2022
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Ingår i: Evolutionary Applications. - : Wiley. - 1752-4571. ; 16:2, s. 311-20
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Tidskriftsartikel (refereegranskat)abstract
- Marine microorganisms have the potential to disperse widely with few obvious barriers to gene flow. However, among microalgae, several studies have demonstrated that species can be highly genetically structured with limited gene flow among populations, despite hydrographic connectivity. Ecological differentiation and local adaptation have been suggested as drivers of such population structure. Here we tested whether multiple strains from two genetically distinct Baltic Sea populations of the diatom Skeletonema marinoi showed evidence of local adaptation to their local environments: the estuarine Bothnian Sea and the marine Kattegat Sea. We performed reciprocal transplants of multiple strains between culture media based on water from the respective environments, and we also allowed competition between strains of estuarine and marine origin in both salinities. When grown alone, both marine and estuarine strains performed best in the high-salinity environment, and estuarine strains always grew faster than marine strains. This result suggests local adaptation through countergradient selection, that is, genetic effects counteract environmental effects. However, the higher growth rate of the estuarine strains appears to have a cost in the marine environment and when strains were allowed to compete, marine strains performed better than estuarine strains in the marine environment. Thus, other traits are likely to also affect fitness. We provide evidence that tolerance to pH could be involved and that estuarine strains that are adapted to a more fluctuating pH continue growing at higher pH than marine strains.
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| 32. |
- Sjoqvist, C., et al.
(författare)
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Effects of Grazer Presence on Genetic Structure of a Phenotypically Diverse Diatom Population
- 2014
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Ingår i: Microbial Ecology. - : Springer Science and Business Media LLC. - 0095-3628 .- 1432-184X. ; 67:1, s. 83-95
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Tidskriftsartikel (refereegranskat)abstract
- Studies of predator-prey systems in both aquatic and terrestrial environments have shown that grazers structure the intraspecific diversity of prey species, given that the prey populations are phenotypically variable. Populations of phytoplankton have traditionally considered comprising only low intraspecific variation, hence selective grazing as a potentially structuring factor of both genetic and phenotypic diversity has not been comprehensively studied. In this study, we compared strain specific growth rates, production of polyunsaturated aldehydes, and chain length of the marine diatom Skeletonema marinoi in both grazer and non-grazer conditions by conducting monoclonal experiments. Additionally, a mesocosm experiment was performed with multiclonal experimental S. marinoi populations exposed to grazers at different levels of copepod concentration to test effects of grazer presence on diatom diversity in close to natural conditions. Our results show that distinct genotypes of a geographically restricted population exhibit variable phenotypic traits relevant to grazing interactions such as chain length and growth rates. Grazer presence affected clonal richness and evenness of multiclonal Skeletonema populations in the mesocosms, likely in conjunction with intrinsic interactions among the diatom strains. Only the production of polyunsaturated aldehydes was not affected by grazer presence. Our findings suggest that grazing can be an important factor structuring diatom population diversity in the sea and emphasize the importance of considering clonal differences when characterizing species and their role in nature.
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| 33. |
- Sjoqvist, C., et al.
(författare)
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Local adaptation and oceanographic connectivity patterns explain genetic differentiation of a marine diatom across the North Sea-Baltic Sea salinity gradient
- 2015
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Ingår i: Molecular Ecology. - : Wiley. - 0962-1083 .- 1365-294X. ; 24:11, s. 2871-2885
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Tidskriftsartikel (refereegranskat)abstract
- Drivers of population genetic structure are still poorly understood in marine micro-organisms. We exploited the North Sea-Baltic Sea transition for investigating the seascape genetics of a marine diatom, Skeletonema marinoi. Eight polymorphic microsatellite loci were analysed in 354 individuals from ten locations to analyse population structure of the species along a 1500-km-long salinity gradient ranging from 3 to 30psu. To test for salinity adaptation, salinity reaction norms were determined for sets of strains originating from three different salinity regimes of the gradient. Modelled oceanographic connectivity was compared to directional relative migration by correlation analyses to examine oceanographic drivers. Population genetic analyses showed distinct genetic divergence of a low-salinity Baltic Sea population and a high-salinity North Sea population, coinciding with the most evident physical dispersal barrier in the area, the Danish Straits. Baltic Sea populations displayed reduced genetic diversity compared to North Sea populations. Growth optima of low salinity isolates were significantly lower than those of strains from higher native salinities, indicating local salinity adaptation. Although the North Sea-Baltic Sea transition was identified as a barrier to gene flow, migration between Baltic Sea and North Sea populations occurred. However, the presence of differentiated neutral markers on each side of the transition zone suggests that migrants are maladapted. It is concluded that local salinity adaptation, supported by oceanographic connectivity patterns creating an asymmetric migration pattern between the Baltic Sea and the North Sea, determines genetic differentiation patterns in the transition zone.
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| 34. |
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"Theme Section 2: Specfic 2021: Time and History"
- 2022
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- A theme section in Fafnir based on four contributions from the conference "SpecFic2021: Time and History", Karlstad University December 1-3 2021, edited by Godhe, Oakes & Varis.
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